Laundry appliance

ABSTRACT

A laundry appliance such as a washing machine includes an outer housing and a drum rotatably mounted therein. The drum has an inner wall and an outer wall separate from the inner wall, the inner and outer walls being perforated to allow washing liquid to flow into and out of the drum via the perforations. The area of the perforations per unit area of the outer wall is greater than the area of the perforations per unit area of the inner wall.

FIELD OF THE INVENTION

The invention relates to a laundry appliance. Particularly, but notexclusively, the invention relates to a washing machine.

BACKGROUND OF THE INVENTION

A washing machine generally consists of an outer casing in which ismounted a water-tight interior container or tub. A perforated drum iscommonly mounted inside the tub in a manner which allows the drum torotate with respect to the tub. During operation, washing liquid iscontained within the tub and the laundry to be washed is located withinthe perforated drum. The laundry is agitated, either by slow rotation ofthe drum or by the operation of an agitator located within the drum.When the laundry has been washed, some washing liquid is drained fromthe tub and further washing liquid is extracted from the laundry byspinning of the drum within the interior container to spin washingliquid therefrom. The extracted water exits the drum through theperforations in the wall thereof. Extraction of rinse water is achievedin a similar manner.

It is understood that more water can be extracted from the laundry ifthe drum is spun at higher spin speeds. There is thus a tendency to spinthe drum at as high a spin speed as possible. Increasing the spin speed,however, results in the need for a stronger drum. One way to achievethis is to manufacture the drum with an inner wall and an outer wall. Adrum having this type of configuration is illustrated in WO 99/58753.There is a risk, however, that water which is being spun out of the drumduring the spinning stage of a washing cycle will be retained betweenthe inner and outer walls of the drum. This would add to the effectiveweight of the drum and result in excessive consumption of energy.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laundry appliancein which the drum is arranged so as to have adequate strength towithstand the stresses imposed on it at high spin speeds and also toallow the egress of water or washing liquid from the interior of thedrum through the perforated walls in a manner which discourages waterretention between the inner and outer walls. It is a further object ofthe present invention to provide a laundry appliance in which the drumhas an outer wall and an inner wall and water egress therethrough is atleast as rapid as it would be through a drum having only a single wall.

The invention provides a laundry appliance comprising an outer housingand a drum mounted rotatably therein, the drum comprising an inner walland an outer wall, the inner and outer walls being perforated to allowwashing liquid to flow into and out of the drum via the perforations,characterised in that the area of the perforations per unit area of theouter wall is greater than the area of the perforations per unit area ofthe inner wall.

The provision of two separate walls of the drum maintains the strengththereof. The provision of perforations in the outer wall having an areaper unit area of the outer wall greater than the corresponding area ofthe perforations in the inner wall reduces the risk of water beingretained within the space between the inner and outer walls.

Preferably, the total area of the perforations in the outer wall perunit area thereof is at least 10% bigger than the total area of theperforations in the inner wall per unit area thereof. More preferably,the total area of the perforations in the outer wall per unit areathereof is at least 20% bigger than the total area of the perforationsin the inner wall per unit area thereof. The comparatively large area ofthe perforations in the outer wall is useful in preventing waterbuild-up in the space between the inner and outer walls.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic sectional side view of a laundry applianceaccording to the invention;

FIG. 2 is a schematic sectional side view of an alternative embodimentof the laundry appliance shown in FIG. 1;

FIG. 3 is a sectional view, shown on a greatly enlarged scale, of aportion of a drum forming part of the washing machine shown in either ofFIGS. 1 and 2;

FIG. 4 is a plan view of the wall portion shown in FIG. 3 showing thehole configuration thereof;

FIG. 5 is a plan view, similar to FIG. 4, of an alternative wall portionhaving a first alternative hole configuration; and

FIGS. 6 to 9 are further plan views, similar to FIGS. 4 and 5, offurther alternative wall portions having second, third, fourth and fifthalternative hole configurations.

DETAILED DESCRIPTION OF THE INVENTION

A laundry appliance in the form of a washing machine 100 is shown inschematic sectional side view in FIG. 1. The washing machine 100comprises an outer casing 102 which is supported on feet 104. Awater-tight tub 106 is mounted inside the outer casing 102 by means ofsprings 108 and dampers 110 in a known manner. In this way, the tub 106is able to move within certain limits with respect to the outer casing102. A water inlet 112 communicates with an upper portion of the tub 106and is connectable (by connection means not shown) to a suitable watersupply. A water outlet 114 communicates with the bottom of the tub 106and has a water pump 116 located therein so that water can be drainedfrom the tub 106 to a suitable drain. A door 118 is located in the frontof the outer casing 102 so as to provide access to the interior of thetub 106. A flexible seal 120 is provided between the tub 106 and thedoor 118 when the door 118 is in its closed position.

A drum 122 is rotatably mounted inside the tub 106. The drum 122 issupported in cantilever fashion on a shaft 124 which, in turn, isrotatably supported on the tub 106 by bearings 126. A motor 128 isprovided inside the outer casing 102 and is connected in suitablefashion to the shaft 124 in order to effect rotation of the drum 122about its own longitudinal axis. The drum 122 has cylindrical walls 130which are perforated so as to allow water to pass through thecylindrical walls 130 of the drum 122.

The features of the washing machine described 100 thus far are known. Inoperation, articles to be washed are introduced to the interior of thedrum 122 via the door 118. Thereafter, the door 118 is closed. Water isthen introduced to the tub 106 via the water inlet 112. Detergent isintroduced to the interior of the tub 106 in any of a variety of knownways (e.g. via a soap tray, detergent ball or tablets). As the waterlevel in the tub 106 rises, water enters the interior of the drum 122via the perforations in the cylindrical walls 130 and wets the articlesto be washed. A washing action is carried out by operation of the motor128 which causes the drum 122 to rotate about its own longitudinal axisinside the tub 106. The speed of rotation is chosen so that the wetarticles are lifted out of the washing liquid and subsequently droppedback thereinto. This known action effectively removes dirt from thearticles to be washed.

When the washing portion of the cycle is complete, the pump 116 isoperated so that water is drained from the lower part of the tub 106 andpassed to a drain via the water outlet 114. Washing liquid is furtherextracted from the wet laundry articles by increasing the speed ofrotation of the drum 122 so that water is centrifugally extracted fromthe laundry articles and flung outwardly through the perforations in thecylindrical walls 130. Water thus extracted drains to the lower portionof the tub 106 and is then pumped away to the drain via the water outlet114. Rinse water is then introduced to the tub 106 via the water inlet112, a tumbling action is carried out so as to extract detergent fromthe laundry articles and the rinse water is then drained and spun out ofthe laundry articles as described above. This rinsing procedure iscommonly repeated at least three times.

The method outlined above is not new. Modifications to and variations onthe washing machine 100 and the method just described above are wellknown in the art and can be incorporated into the washing machine 100and its operation without departing from the scope of the invention.

The present invention relates to the construction of the drum 122,particularly to the construction of the cylindrical walls 130. In orderto reduce the time required to dry articles which have been washed by anautomatic washing machine, there is a general desire to increase thespeed at which the drum of the washing machine rotates or spins.Increasing the spin speed generally extracts more water from the laundryarticles and therefore drying can be achieved in a shorter time.However, increasing the spin speed necessitates some strengthening ofthe rotatable drum 122. In order to strengthen the drum 122, thecylindrical wall 130 consists of an inner wall 132 and an outer wall134, in contrast to a cylindrical wall having a single layer.

The inner wall 132 lies parallel to the outer wall 134 and, in theembodiment shown in FIG. 1, the inner wall 132 extends across the entiredepth of the drum 122. In an alternative embodiment, shown in FIG. 2,the drum arrangement is slightly different. Whilst all other componentsshown in FIG. 2 remain identical to those illustrated in FIG. 1, thedrum 222 shown in FIG. 2, and its support means, are not. Specifically,the drum 222 comprises a first rotatable portion 222 a and a secondrotatable portion 222 b. The first rotatable portion 222 a is rotatablysupported in cantilever fashion, as before, by way of a first shaft 224a. The second rotatable portion 222 b is also supported in cantileverfashion, this time on a second shaft 224 b, which is rotatably mountedinside the first shaft 224 a. The second rotatable portion 222 b islocated inside the first rotatable portion 222 a at the end thereofadjacent the shafts 224 a,224 b. The motor 228 is arranged so as to beable to drive the rotatable portions 222 a,222 b by way of the shafts224 a,224 b so that relative rotation therebetween is achieved. Thedetails and advantages of such an arrangement are set out and describedin detail in WO99/58753.

The second rotatable portion 222 b extends across approximately one halfof the depth of the drum 222. In the area in which the second rotatableportion 222 b is provided (ie. the area adjacent the shafts 224 a,224b), the second rotatable portion 222 b forms an inner wall 232. Radiallyoutwardly of the second rotatable portion 222 b, lies part of the firstrotatable portion 222 a. This part of the first rotatable portion 222 aforms an outer wall 234. Beyond the furthest extent of the secondrotatable portion 222 b, the first rotatable portion 222 a has aconstruction similar to that shown in FIG. 1, i.e. the first rotatableportion 222 a has a cylindrical wall 230 comprising an inner wall 232 aand an outer wall 234 a.

As can be seen from the forgoing descriptions, most, if not all, of thecylindrical wall of the drum 122,222 comprises an inner wall 132,232,232a and an outer wall 134,234,234 a. In the embodiment shown in FIG. 1,the inner wall 132 and the outer wall 134 are fixedly joined together sothat the inner and outer walls 132,134 rotate together. Although theconfiguration of the embodiment shown in FIG. 2 allows the first andsecond rotatable portions 222 a,222 b to rotate independently of oneanother, the washing machine 200 will be configured and arranged so thatthe first and second rotatable portions 222 a,222 b of the drum 222 willbe rotated at the same speed and in the same direction during anyspinning steps of the washing cycle. Thus, the first and secondrotatable portions 222 a,222 b will behave as a single unit during thewater extraction steps. In either embodiment, water extracted from thelaundry articles must therefore pass through both the inner wall132,232,232 a and the outer wall 134,234,234 a during spinning.

FIG. 3 shows, on a greatly enlarged scale, part of an inner wall 32 andan outer wall 34 which could be used in either of the washing machines100,200 illustrated in FIGS. 1 and 2. Both walls 32,34 are made frommetal (e.g. stainless steel) and have appropriate perforations formedtherein by either punching or stamping. The inner wall 32 comprises anarray of perforations 42 and the outer wall 34 comprises an array ofperforations 44. Arrow 46 indicates the direction of water flow during aspinning step of the washing procedure.

FIG. 4 is a plan view, looking along the arrow 46, of the inner wall 32shown in FIG. 3. The perforations 42 are shown in bold lines with theperforations 44 formed in the outer wall 34 shown in dotted lines. Ascan be seen, the perforations 42 in the inner wall 32 form a regulararray of holes having a 5 mm diameter and spaced 2 cm apart inhorizontal rows. The rows of perforations 42 are spaced 1.5 cm apart andalternate rows are offset by 1 cm with respect to the adjacent rows. Theperforations 44 located in the outer wall 34 are arranged in anidentical array but have a diameter of 10 mm. Thus, the total area ofthe perforations 44 in the outer wall 34 per unit area thereof is fourtimes larger than the total area of the perforations 32 in the innerwall 32 per unit area thereof.

An alternative arrangement is illustrated in FIG. 5. In FIG. 5, thearray of perforations 42 a in the inner wall 32 is identical to that ofthe perforations 42 shown in FIG. 4. The array of perforations 44 aformed in the outer wall 34 is similar to that of the perforations 44shown in FIG. 4, except that alternate perforations 44 a are omitted.Thus, a perforation 44 a is provided in respect of only alternateperforations 42 a. The total area of the perforations 44 a in the outerwall 34 per unit area thereof is thus only twice as large as the totalarea of the perforations 42 a in the inner wall 32 per unit areathereof.

In the arrangements shown in FIGS. 3, 4 and 5, each perforation 44, 44 ain the outer wall 34 is radially aligned with a perforation 42,42 a inthe inner wall 32. By this we mean that, if a line were to be drawnradially from the axis of rotation of the drum 122,222 through thecentre of any one of the perforations 44,44 a in the outer wall 34, thenit would have already passed through the centre of a perforation 42,42 ain the inner wall 32 by the time it reached the outer wall 34.

Radial alignment is, however, not essential to this invention. FIG. 6shows a second alternative arrangement in which the array ofperforations 42 b in the inner wall 32 is the same as that shown inFIGS. 4 and 5. Again, the diameter of each perforation 42 b is 5 mm.However, the array of perforations 44 b arranged in the outer wall 34 isdifferent from either of those shown in FIGS. 4 and 5. In thisembodiment, the perforations 44 b are offset from the perforations 42 bin the inner wall 32 by 1 cm. Furthermore, the diameter of theperforations 44 b is 6 mm. This results in the total area of theperforations 44 b in the outer wall 34 per unit area thereof beingapproximately 40% greater than the total area of the perforations 42 bin the inner wall 32 per unit area thereof.

A further alternative configuration is illustrated in FIG. 7. Onceagain, the array of perforations 42 c formed in the inner wall 32 is thesame as that illustrated in FIGS. 4, 5 and 6. However, the array ofperforations 44 c formed in the outer wall 34 is different. As in theembodiment illustrated in FIG. 6, the diameter of the perforations 44 cis 6 mm. However, there are fewer perforations 44 c formed in the outerwall 34 as illustrated in FIG. 7. In this arrangement, only threeperforations 44 c are provided for every four perforations 42 c. Thisarrangement gives a total area of the perforations 44 c in the outerwall 34 per unit area thereof of approximately 10% more than the totalarea of the perforations 42 c in the inner wall 32 per unit areathereof.

A third alternative embodiment is illustrated in FIG. 8. In thisembodiment, the array of perforations 42 d formed in the inner wall 32comprises rows of perforations 42 d of 3 mm diameter spaced aparthorizontally by a distance of 1 cm. Adjacent rows are spaced verticallyby a distance of 8.5 mm and offset by a distance of 5 mm. The array ofperforations 44 d formed in the outer wall 34 is made up of horizontalrows of perforations 44 d of 8 mm diameter and spaced apart by 2.5 cm.Adjacent rows, which are not offset, are spaced apart by 2.7 cm. In thisembodiment, the total area of the perforations 44 d in the outer wall 34per unit area thereof is approximately 5% greater than the total area ofthe perforations 42 d in the inner wall 32 per unit area thereof.

A fourth alternative embodiment is illustrated in FIG. 9. Thisembodiment is similar to that shown in FIG. 8 except that, in FIG. 9,the diameter of the perforations 44 e formed in the outer wall 34 is 11mm instead of 8 mm. This arrangement provides a total area of theperforations 44 e in the outer wall 34 per unit area thereof which isapproximately twice the total area of the perforations 42 e in the innerwall 32 per unit area thereof.

It will be appreciated that the structure and specific features of thewashing machine 100,200 described above are mostly irrelevant to thepresent invention. Therefore, alternative constructions of the supportbearings, shafts, water inlet, water drain, door, etc and methods ofoperation can be provided without departing from the scope of theinvention. The invention relates simply to the construction of thecylindrical walls of the drum and features which do not relate to thisare regarded as inessential to the invention.

By providing an array of perforations in the outer wall of the drumwhich has a total area of perforation per unit area of the said wallwhich is greater than the area of the perforations provided in the innerwall per unit area thereof, it is perceived that the likelihood of buildup of water between the inner and outer walls during extractiontherethrough will be reduced.

1. A laundry appliance comprising an outer housing defining a washingspace, a drum mounted rotatably in the outer housing and a door in theouter housing closing the washing space, the drum comprising an innerside wall and an outer side wall separate from the inner side wall, theinner and outer side walls being perforated to allow washing liquid toflow into and out of the drum via the perforations, wherein the area ofthe perforations per unit area of the outer side wall is greater thanthe area of the perforations per unit area of the inner side wall.
 2. Alaundry appliance as claimed in claim 1, wherein all of the perforationsare circular.
 3. A laundry appliance as claimed in claim 1 or 2, whereinthe perforations in the inner side wall are all the same size.
 4. Alaundry appliance as claimed in claim 3, wherein all of the perforationsin the outer side wall are larger than any of the perforations in theinner side wall.
 5. A laundry appliance as claimed in claim 4, whereinthe total area of the perforations in the outer side wall per unit areathereof is at least 10% greater than the total area of the perforationsin the inner side wall per unit area thereof.
 6. A laundry appliance asclaimed in claim 5, wherein the total area of the perforations in theouter side wall per unit area thereof is at least 20% greater than thetotal area of the perforations in the inner side wall per unit areathereof.
 7. A laundry appliance as claimed in claim 1 or 2, wherein theperforations in the outer side wall are all the same size.
 8. A laundryappliance as claimed in claim 7, wherein all of the perforations in theouter side wall are larger than any of the perforations in the innerside wall.
 9. A laundry appliance as claimed in claim 8, wherein each ofthe perforations in the outer side wall is larger than each of theperforations in the inner side wall.
 10. A laundry appliance as claimedin claim 9, wherein the total area of the perforations in the outer sidewall per unit area thereof is at least 10% greater than the total areaof the perforations in the inner side wall per unit area thereof.
 11. Alaundry appliance as claimed in claim 9, wherein the total area of theperforations in the outer side wall per unit area thereof is at least20% greater than the total area of the perforations in the inner sidewall per unit area thereof.
 12. A laundry appliance as claimed in claim8, wherein each perforation in the outer side wall is radially alignedwith one of the perforations in the inner side wall.
 13. A laundryappliance as claimed in claim 8, wherein each of the perforations in theouter side wall is larger than each of the perforations in the innerside wall.
 14. A laundry appliance as claimed in claim 1 or 2, whereineach perforation in the outer side wall is radially aligned with one ofthe perforations in the inner side wall.
 15. A laundry appliance asclaimed in claim 1 or 2, wherein all of the perforations in the outerside wall are larger than any of the perforations in the inner sidewall.
 16. A laundry appliance as claimed in claim 1 or 2, wherein theinner side wall is rigidly attached to the outer side wall and isrotatable therewith.
 17. A laundry appliance, comprising an outerhousing and a drum mounted rotatably therein, the drum comprising aninner side wall and an outer side wall separate from the inner sidewall, the inner and outer side walls being perforated to allow washingliquid to flow into and out of the drum via the perforations, whereinthe area of the perforations per unit area of the outer side wall isgreater than the area of the perforations per unit area of the innerside wall and wherein the inner side wall is rotatably mounted so as tobe rotatable separately from the outer side wall.
 18. A laundryappliance as claimed in claim 1 or 2, further comprising a watertighttub in which the drum is rotatably mounted, and wherein the drum isrotatable about an axis which is substantially horizontal.
 19. A laundryappliance comprising an outer housing and a drum mounted rotatablytherein, the drum comprising an inner side wall and an outer side wall,the inner and outer side walls being perforated to allow washing liquidto flow into and out of the drum via the perforations and the inner sidewall being rotatable at least in part relative to the outer side wallwherein the area of the perforations per unit area of the outer sidewall is greater than the area of the perforations per unit area of theinner side wall.
 20. A laundry appliance as claimed in claim 19, whereinall of the perforations are circular.
 21. A laundry appliance as claimedin claim 19 or 20, wherein the perforations in the inner side wall areall the same size.
 22. A laundry appliance as claimed in claim 19 or 20,wherein the perforations in the outer side wall are all the same size.23. A laundry appliance as claimed in claim 19 or 20, wherein all of theperforations in the outer side wall are larger than any of theperforations in the inner side wall.
 24. A laundry appliance as claimedin claim 23, wherein the total area of the perforations in the outerside wall per unit area thereof is at least 10% greater than the totalarea of the perforations in the inner side wall per unit area thereof.25. A laundry appliance as claimed in claim 23, wherein the total areaof the perforations in the outer side wall per unit area thereof is atleast 20% greater than the total area of the perforations in the innerside wall per unit area thereof.
 26. A laundry appliance as claimed inclaim 19 or 20, wherein each perforation in the outer side wall isradially aligned with one of the perforations in the inner side wall.